1. Field of the Invention
The present invention provides a polarization converter and a projector apparatus comprising the same. More particularly, the present invention provides a polarization converter and a projector apparatus capable of improving the optical efficiency and with a low cost.
2. Descriptions of the Related Art
Solid-state light sources, such as light emitting diodes (LEDs) or laser diodes (LDs), have a long service life, a small volume and are free of mercury. However, when the solid-state light sources are used as light sources in projector apparatuses, the brightness provided by the solid-state light sources is still considerably lower than that provided by conventional high-pressure mercury lamps. Therefore, despite the widespread use of solid-state light sources, they have not yet completely replaced conventional high-pressure mercury lamps in the field of projector apparatuses.
Furthermore, because projection systems adopting high-pressure mercury lamps generally emit light rays of ultraviolet (UV) wavelengths that may impair the viewers' vision, a UV light filter must be additionally disposed at an extra cost in the projection systems to filter the UV light rays that are harmful to human eyes. For this reason, high-pressure mercury lamps have been replaced by LEDs or LDs in most of the current projection systems to miniaturize the projection systems.
On the other hand, projection systems adopting digital light processing (DLP) technologies have become the mainstream products in the projector market due to their advantages such as high brightness, realistic colors, fast response and light weight. Nowadays, applications of DLP projection systems have gradually extended to the field of stereoscopic displaying projections. Generally, to perform beam splitting on a stereoscopic image in a single projector, a conventional DLP projection system often uses a rotary optical filtering wheel that rotates synchronously with a color wheel to provide split images of different wavelength regions to the left eye and the right eye respectively so that a left image is received by the left eye and a right image is received by the right eye to generate a stereoscopic image. However, it is difficult for the rotary optical filtering wheel of the conventional stereoscopic imaging technologies to rotate in optimal synchronism with the color filter no matter the rotational speed or the rotation angle.
Furthermore, most stereoscopic displaying projection systems adopting DLP technologies must be used in combination with a pair of active glasses that is relatively expensive, which makes it difficult to lower the overall cost of such stereoscopic displaying projection systems. Moreover, the left and right shutter switching technology adopted in active glasses that is currently available has a drawback in that it may decrease the brightness of the left-eye and the right-eye view-angle images during operation.
Furthermore, in conventional stereoscopic displaying technologies (e.g., that utilize polarized light with an S polarized direction or a P polarized direction), it is likely that the user who wears such a pair of glasses sees two images at the same time due to an incomplete sheltering of the left-eye and the right-eye images when the user's head tilts (e.g., the angle of lenses of the glasses is inconsistent with a preset direction of the optical system). This causes an image cross-talk problem from which the stereoscopic displaying technologies have suffered for a long period of time.
Accordingly, an urgent need exists in the art to solve the aforesaid problems and drawbacks by designing a stereoscopic projection system that can be used with a pair of passive glasses and that has a low cost, a simplified optical arrangement, a miniaturized volume and an improved optical efficiency (e.g., an improved brightness).